The Pediatric Tumor Biology and Ultrastructural Pathology (UP) Section has the following functions: (A) it provides specialized diagnostic services for cases difficult to classify with conventional methods; (B) it provides diagnostic consultative services to the Pediatric Branch (PB) at the National Cancer Institute (NCI) and participates in a weekly PB Tumor Staging Conference; and (C) it is engaged in independent and collaborative research with the ultimate goal to improve available diagnostic techniques for the classification of poorly differentiated solid pediatric tumors and to define prognostic factors which may lead to development of new therapeutic strategies.